There are currently available on the market certain highly pure alpha alumina monohydrates which are particularly characterized by their high content of alpha alumina monohydrate and by their low content of other forms of alumina. In many instances, the purity of these materials may approach 100% alpha alumina monohydrate.
It is a particular feature of these aluminas that they are substantially free of (or at least contain a very low content of) impurities which are usually found in prior art aluminas -- and the most common of these impurities is sodium.
These aluminas are typically recovered as by products of the so-called Ziegler syntheses -- in particular the Ziegler synthesis of higher alcohols -- see for example U.S. Pat. No. 2,892,858 which discloses an illustrative process. The Ziegler process typically uses a catalyst containing a titanium composition, such as titanium tetrachloride, and an aluminum compound such as diethyl aluminum chloride.
Upon completion of the Ziegler reactions, the catalyst may ultimately be recovered as and converted to a pure alpha alumina monohydrate which contains titanium as the principal impurity -- typically in amount of 150-700, say 600 ppm.
The commonly available Catapal S grade of alumina, derived from by-product recovery of Ziegler catalyst typically contains (in addition to titanium as noted supra) 80-120 ppm, say about 100 ppm silicon; 27-61 ppm, say 40 ppm of iron; 14-70 ppm, say 50 ppm of magnesium; and alkali metals including sodium at a level which is too low to be detected by the usual gravimetric methods of analysis.
Such aluminas, typified by Catapal S, would be expected to be of high utility as catalyst supports. This is in fact not found to be the case. It appears that catalyst pellets formed from these aluminas are less than fully satisfactory because the pellets exhibit an undesirably high tendency to produce fines resulting from the physical deterioration of the pellet.